The present invention relates generally to an apparatus for moving a window into an open or closed position. In particular, the present invention relates to a mechanism for use with an automobile window, wherein the mechanism utilizes pinion gears with resilient shock absorbers to cushion the system from disturbances, a clutch mechanism to prevent back-drive of the worm gear and a support bracket that allows the window to find the path of least resistance during closure.
Modern automobiles typically include a window lift assembly for raising and lowering windows in the door of the vehicle. A common type of window lift assembly incorporates a xe2x80x9cscissor mechanism.xe2x80x9d A scissor-type system utilizes a series of linkages in a scissor configuration such that as the bottom linkages move apart, the top linkages do as well, resulting in a scissor-like motion. The window is fastened to a bracket connected to a linkage. A motor and gearset drives the scissor mechanism in power operated window mechanisms.
The scissor-type mechanism is typically mechanically inefficient, prohibiting the use of light-weight materials and requiring the use of relatively large motors to drive the system. The large motors necessarily require increased space and electrical power and also increase the weight of the system. With the limited space in a scissor-type system it is also necessary, in order to provide the required torque transfer efficiency and acceptable up and down times (3-4 seconds), to have a small diameter pinion gear, typically 0.5 to 0.75 inches, and relatively large worm gear, typically 1.8 to 2.5 inches in diameter, with gear ratios of 9 to 16 and 80 to 90, respectively. This results in excessive worm gear speed in the range of 3000 to 4000 RPM which causes excessive worm gear tooth shock and armature noise. The combination of high torque, typically 80 to 125 inch-pounds at stall, and shock due to high worm speeds mandates that either expensive multiple gears and/or single worm gears with integral shock absorbers be utilized.
Further, the scissor-type mechanism does not take into account the manufacturing deviations in the door, specifically with the window frame and mounting points, and deviations in the manufacture of the scissor-type mechanism. Deviations in the door and scissor-type mechanism result in larger than necessary forces being applied to the window when it cycles up and down. The larger force on the window causes undesirable noise in the passenger cabin.
Accordingly, a need exists for a window lift mechanism with increased efficiency that would allow for a reduction in the motor size and hence the mass of the system, and a support structure for the window that permits the window to find the path of least resistance when it cycles up and down.
The present invention provides a window lift mechanism for an automobile window. The window lift mechanism of the present invention has a gear set with at least one pinion gear and at least one worm gear operatively coupled together and supported by the window. The gear set is driven by a motor with an output shaft having a worm which engages the worm gear. The window lift mechanism utilizes a clutch mechanism to increase the efficiency of the torque transfer from the motor to the worm gear in the gear set. The clutch mechanism includes a pair of springs located within the worm gear. This clutch mechanism prevents back drive, hence allowing for the worm on the output shaft of the motor to have a lead angle greater than seven degrees. With a larger worm angle, the amount of torque transferred from the worm to the worm gear is increased, allowing for a smaller motor. The smaller motor reduces the mass of the system.
Further, the gear set in the window lift mechanism of the present invention has a resilient shock absorber operatively engaged between the pinion gear and the worm gear. The shock absorber has surfaces with notched portions to allow for deformation of the resilient shock absorber, which reduces unwanted stress in the gear set and thereby increases the life of the gears.
The window lift mechanism of the present invention has two support structures, the first support is coupled to the closure member and the second support is coupled to the first support. The second support houses a portion of the gear set. There is an interface between the first and second supports which permits axial and rotational movement of the window with respect to the second support. Specifically, the first support has a forked side coupled to the window and a slot for receipt of a protrusion from the second support. The allowed movement of the window allows the closure member to find the path of least resistance during closure, and aids in overcoming manufacturing imperfections.